It is well known that desiccant materials are utilized within desiccant containers to remove moisture, oxygen, or other gases from a product while the product is packaged prior to usage by a consumer. Known desiccant containers include bags, odor absorbent packages, fragrance sachets, vapor corrosion inhibitor (“VCI”) packaging, oxygen scavenging packets, and solid cylindrical canisters typically made of a translucent molded plastic having breathable ends. The most common use of desiccant materials is for pharmaceutical applications wherein a desiccant container is inserted within a bottle or other container of a pharmaceutical product to adsorb moisture and gasses. Silica crystals or powder is a typical desiccant material within the containers for such pharmaceutical usage.
There are literally dozens of other known desiccant materials, including for example activated alumina for drying gasses. Activated carbon has been used as an adsorbent for odors and toxic gases, and has been used in military gas masks. Other desiccant materials include metal salts, phosphorous compounds, activated charcoal, crystalline metal aluminosilicates, activated bentonites, silica gel, calcium sulfate, known molecular sieves, etc. For purpose herein, the phrase “desiccant material” will mean any material known in the art such as those recited above that is capable of removing an unwanted gaseous compound or molecules from a specific environment.
Typically, a selected desiccant material is placed within one of two forms of common desiccant containers. One form of desiccant container is a flexible bag that is formed of a breathable material, wherein gaseous exchange may occur through the entire container except through sealed ends of the bag or packet. A more common form of desiccant container is a cylindrical-shaped canister made of solid molded plastic having one or two breathable ends. U.S. Pat. No. 5,759,241 that was issued on Jun. 2, 1998 shows such a solid canister, wherein at least one breathable end includes perforations. A disk-shaped, fine pore member is secured to the end overlying the perforations to prohibit dusting or passage of fine particulates of the desiccant material from the canister onto the products, such as pharmaceutical pills, in a container housing the desiccant canister. The disk-shaped material is disclosed in that Patent as preferably made of a spun bonded polyolefin available under the trademark “TYVEK” from the E.I. Dupont Company of Wilmington, Del., U.S.A. (For purposes herein, a material that is characterized as “breathable” and that also has a sufficiently small pore size range to prohibit passage of liquid water and dusting of fine particulates will be hereafter characterized as being “gas permeable and liquid impermeable”.)
Significant problems are associated with the selection of a form and size of a desiccant container because of inherent structural limitations of known cylindrical desiccant canisters. The cylindrical canisters are best suited for automated, high-speed insertion of the canisters into pharmaceutical bottles within specialized packaging machinery. Desiccant containers that are made of elongate bags secured together in a long strip of such bags pose a significant risk of being cut through the bag resulting in a spill of the desiccant material onto the packaging machine and possibly into the medicine bottle. Consequently, they are increasingly dis-favored as packaging machinery becomes ever-more efficient and high speed. Additionally, the large, distinctive cylindrical shape makes the plastic canister form of desiccant container clearly different than ordinary pharmaceutical pill shapes within medicine bottles, thus preventing accidental ingestion. However, because the molded cylindrical bodies of the desiccant canisters are made of a solid, gas and liquid impermeable material, and because they only provide for gaseous exchange through very fine pore, liquid impermeable ends to restrict passage of fine particles of the desiccant material out of the container, a rate of gaseous exchange and moisture passage through the canisters is necessarily restricted. Consequently, for a specific moisture or gas-cleaning requirement, cylindrical desiccant containers of solid plastic must be quite large to provide for adequate movement of gas into and out of the canister.
Manufacture of such molded plastic desiccant canisters typically involves injection of plastic into a mold of a cylindrical body. The body is then filled with the desiccant material, and then a cap, such as the perforated cap and disk-like dust barrier of the aforesaid U.S. Pat. No. 5,759,241, is secured to the body. While the resulting cylindrical, rigid, plastic desiccant containers are effective, the complicated manufacture and assembly of such desiccant containers significantly raises the cost of the containers to as high as about $0.20 (twenty cents U.S.) each. As an example of the scope of the demand for desiccant containers for pharmaceutical medicine bottles, it is generally known that a modern automated packaging machine for filling medicine bottles will insert such desiccant canisters at a rate in excess of 300 canisters per minute. It is estimated that current demand for known desiccant containers is in excess of 750,000,000 per year, and that number is expected to double in the near future.
Accordingly, there is a need for a desiccant container that has a low-cost to manufacture, that can more efficiently hold a desiccant material without a need for complicated manufacture and assembly of dust-passage restricting components, and that can be readily used within modern, high-speed packaging machinery.